1. Field of the Invention
The present invention relates to a nitride semiconductor light-emitting diode.
2. Description of the Related Art
Recently, a nitride semiconductor light-emitting diode having a principal plane of an m-plane has been researched and developed actively. The reason is because the nitride semiconductor light-emitting diode having a principal plane of an m-plane does not have a piezoelectric field, which decreases a luminous efficiency thereof. Hereinafter, a nitride semiconductor light-emitting diode having a principal plane of an m-plane is referred to as “m-plane nitride semiconductor light-emitting diode”. The m-plane nitride semiconductor light-emitting diode emits a polarized light.
Japanese Patent Laid-Open Publication No. 2013-038208 discloses an m-plane nitride semiconductor light-emitting diode which improves light extraction efficiency. FIG. 10 is a duplicate of FIG. 2 included in Japanese Patent Laid-Open Publication No. 2013-038208. As shown in FIG. 10, the disclosed m-plane nitride semiconductor light-emitting diode 10 comprises an optically-transparent substrate 11, a semiconductor layer 12, an n-electrode 13 and a p-electrode 14. The optically-transparent substrate 11 comprises four inclined surfaces S1-S4.
WO 2012/137406 discloses an m-plane nitride semiconductor light-emitting diode which improves an orientation distribution property. FIG. 11 is a duplicate of FIG. 5 included in WO 2012/137406. As shown in FIG. 11, this disclosed m-plane nitride semiconductor light-emitting diode 300 comprises a p-electrode 308, a p-type semiconductor layer 307, an active layer 306, an n-type semiconductor 306, an n-electrode 309 and a substrate 304. The substrate 304 has an inclined surface 311d which includes a c-axis.